<template>
   <div class="upload-excel">
     <div class="btn-upload">
       <el-button :loading="loading" size="mini" type="primary" @click="handleUpload">
         点击上传
       </el-button>
     </div>
 
     <input ref="excel-upload-input" class="excel-upload-input" type="file" accept=".xlsx, .xls" @change="handleClick">
     <div class="drop" @drop="handleDrop" @dragover="handleDragover" @dragenter="handleDragover">
       <i class="el-icon-upload" />
       <span>将文件拖到此处</span>
     </div>
   </div>
 </template>
 
 <script>
 import * as XLSX from 'xlsx'
 
 export default {
   props: {
     beforeUpload: Function, // eslint-disable-line
     onSuccess: Function// eslint-disable-line
   },
   data() {
     return {
       loading: false,
       excelData: {
         header: null,
         results: null
       }
     }
   },
   methods: {
     generateData({ header, results }) {
       this.excelData.header = header
       this.excelData.results = results
       this.onSuccess && this.onSuccess(this.excelData)
     },
     handleDrop(e) {
       e.stopPropagation()
       e.preventDefault()
       if (this.loading) return
       const files = e.dataTransfer.files
       if (files.length !== 1) {
         this.$message.error('Only support uploading one file!')
         return
       }
       const rawFile = files[0] // only use files[0]
 
       if (!this.isExcel(rawFile)) {
         this.$message.error('Only supports upload .xlsx, .xls, .csv suffix files')
         return false
       }
       this.upload(rawFile)
       e.stopPropagation()
       e.preventDefault()
     },
     handleDragover(e) {
       e.stopPropagation()
       e.preventDefault()
       e.dataTransfer.dropEffect = 'copy'
     },
     handleUpload() {
       this.$refs['excel-upload-input'].click()
     },
     handleClick(e) {
       const files = e.target.files
       const rawFile = files[0] // only use files[0]
       if (!rawFile) return
       this.upload(rawFile)
     },
     upload(rawFile) {
       this.$refs['excel-upload-input'].value = null // fix can't select the same excel
 
       if (!this.beforeUpload) {
         this.readerData(rawFile)
         return
       }
       const before = this.beforeUpload(rawFile)
       if (before) {
         this.readerData(rawFile)
       }
     },
     readerData(rawFile) {
       this.loading = true
       return new Promise((resolve, reject) => {
         const reader = new FileReader()
         reader.onload = e => {
           const data = e.target.result
           const workbook = XLSX.read(data, { type: 'array' })
           const firstSheetName = workbook.SheetNames[0]
           const worksheet = workbook.Sheets[firstSheetName]
           const header = this.getHeaderRow(worksheet)
           const results = XLSX.utils.sheet_to_json(worksheet)
 
           this.generateData({ header, results })
           this.loading = false
           resolve()
         }
         reader.readAsArrayBuffer(rawFile)
       })
     },
     getHeaderRow(sheet) {
       const headers = []
       const range = XLSX.utils.decode_range(sheet['!ref'])
       let C
       const R = range.s.r
       /* start in the first row */
       for (C = range.s.c; C <= range.e.c; ++C) { /* walk every column in the range */
         const cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })]
         /* find the cell in the first row */
         let hdr = 'UNKNOWN ' + C // <-- replace with your desired default
         if (cell && cell.t) hdr = XLSX.utils.format_cell(cell)
         headers.push(hdr)
       }
       return headers
     },
     isExcel(file) {
       return /\.(xlsx|xls|csv)$/.test(file.name)
     }
   }
 }
 </script>
 
 <style scoped lang="scss">
 .upload-excel {
   display: flex;
   justify-content: center;
    margin-top: 100px;
    .excel-upload-input{
        display: none;
         z-index: -9999;
      }
    .btn-upload , .drop{
       border: 1px dashed #bbb;
       width: 350px;
       height: 160px;
       text-align: center;
       line-height: 160px;
    }
    .drop{
        line-height: 80px;
        color: #bbb;
       i {
         font-size: 60px;
         display: block;
       }
    }
 }
 </style>
 